Firing mechanisms for automatic loading arms



' 1956 M. E. MANZO SAL 2,759,399

FIRING MECHANISMS FOR AUTOMATIC LOADING ARMS Filed Dec. 1, 1952 2Sheets-Sheet 1 JNVENTOR.

Aug. 21, 1956 M. E. MANZO SAL FIRING MECHANISMS FOR AUTOMATIC LOADINGARMS Filed Dec. 1, 1952 2 Sheets-Sheet 2 Miguel E. Manzo Sal, Cordoba,Argentina Application December 1, 1952, Serial No. 323,410

12 Claims. (Cl. 89-140) This invention relates to an improved firingmechanism for automatic loading arms, such as submachine guns and thelike firearms and more particularly .it refers to a firing mechanism thenumber of parts of which is considerably smaller than those of at leastmost of the known firing mechanisms for similar type of arms. Still morespecifically this invention relates to a trigger and sear sub-assembly.

It is to be understood that the improved firing mechanism of the presentinvention or more specifically the principle of operation on which saidfiring mechanism is based, may be adapted to a difierent number of firearms such as submachine guns, machine pistols, both of the automatic andsemi-automatic type as well as any other similar small arm.

It is an object of the invention to provide a new type of firingmechanism which is susceptible of economical mass production.

Another object of the invention is to provide a firing mechanism whichwill function in a reliable manner under all=conditions of service.

It is still another object of the invention to provide a firingmechanism which by means of a selector may be used both as an automaticas well as a semi-automatic firing mechanism.

These and further objects and advantages of the pres ent invention willbecome more apparent in the course of the following specificdescription, in which by way of example two specific embodiments aredescribed.

In the drawings:

Figure 1 is a longitudinal vertical sectional view of one of theembodiments of the firing mechanism of the present invention.

Figure 2 is a partial, longitudinal, vertical sectional view of anotherembodiment of the firing mechanism based on the same principle.

Figures 3-6 are schematical longitudinal vertical sectional views,showing four of the main positions of the firing mechanism of Figure 1,when operating as a semiautomatic firing mechanism.

Figures 7 and 8 are schematical longitudinal vertical sectional views,showing two of the main positions of the firing mechanism of Figure 1when operating as an automatic firing mechanism.

Figure 9 is a perspective view of the automatic sear of the firingmechanism of Figure l and in which the this housing 1 is provided withan inertia block 2 that is slidably housed therein and comprisingat-oneend-aspring Patent 2 housing adjacent to the spring guideprojection 3, is, as usually, provided with a cap (not shown) on whichthe bolt and inertia block driving spring 5 butts, against a platform 6.

The inertia block 2 is provided with a sear engaging shoulder 7 adaptedto face an opening .8 of said housing 1 when said inertia block 2 is inits inoperative positions, as will be later explained. The sear engagingshoulder 7 forms .part of a recess 9 in said inertia block 2, theopposite end 10 with regard .to the sear engaging shoulders 7 isconcavely shaped, so that during the backward movement of the inertiablock .2 the heel, as will be later explained may be convenientlyinserted.

The trigger and sear sub-assembly consists of a pivot 11 located outsideof the housing 1 and supporting a semi-automatic sear 12 housed in an atleast partially hollow automatic sear 13 having a trigger 14, as may bealso seen in Figure 9.

The semi-automatic sear 12 comprises at one end a first heel 15 adaptedto engage said sear engaging shoulder 7 and at the opposite end, that isto say on the other side of pivot 11, which operates as a fulcrum, afirst spring housing or casing 16 in which a first compression spring 17is partially housed having a first end 17 butting against the baseportion 16 of said housing 16 and a second end portion 17 buttingagainst a base 18' of a spring guide 18. Said base 18 is suitably fixedto the outer face of said housing 1.

The heel 15 comprises a fiat surface 15' which is substantially parallelwith the sear engaging shoulder 7, when the semi-automatic sear 12 isengaging said shoulder 7. The base portion 12' of the semi-automaticsear 12 is provided with a cylinder 19 having a piston 20 elasticallyurged by spring 21 which is suitably housed in said cylinder 19. One:end 21 of said spring 21 butting against the base 19' :of said cylinder19 whilst the other end 21" of said spring 21 is suitably guided by aspring guide 22 of said piston 20. A stop 23 integral with said cylinder19 limits the forward and backward movements of said piston 20 which hasa recess 24 in which said stop 23 is housed. The head 20 of said :piston.20 emerges out of said cylinder and is adapted to engage the automaticsear 13 in a recess 25 forming partof a friction surface v26.

The automatic sear 13 comprises in this embodiment of Figure l a secondheel v27 which has a Jflat surface 27' of similar inclination as saidflat surface 15' of the semiautomatic sear :12. The automatic sear 13 isalso pro- "guide projection 3 coaxial with the axis 4 "of the inertiablock '2. The opposite end of said inertia block 2 is provided with abolt (not shown). The end of the vi'ded with a second spring housing orcasing 28 located behind the trigger 14 and at the opposite end withregard to pivot 11 in comparison with heel 27 in a similar Waytas thefirst spring housing 16. A second spring guide 29 having .a base 29'operates in connection with a sec- :ond compression spring 30 in asimilar way as the first compression spring 17.

Finally a selector 31 swingab'ly and controllably mounted on a shaft 32supported by the automatic sear 13 and accessible from outside, enablesto control the :semi automatic sear :12 so that the trigger '14 and searmechanism may operate as a semi-automatic or automatic unit as will belater explained.

When the selector .31 is in its inoperative position, as shown inFigures 1 and 3 to 6, vthe trigger and sear mech- .anism operates as asemi-automatic unit. :By semiautomatic unit is .to :be understood anassembly which fires one shot upon each operation of the trigger 14;while an automatic unit is a mechanism which continuously fires, whilethe trigger is pressed and as long as the supply holds.

The operation of the firing mechanism when operating as a semi-automaticunit 'is clearly shown in Figures 3-6, and is as follows:

The inertia block 2 is in its inoperative position, that is to say it islocked by heel 15 of the semi-automatic sear 12, as shown in Figure 3,wherein said inertia block and more particularly the sear engagingshoulder 7 thereof is facing the opening8 of the inertia blockhousing 1. Piston 20 engages the recess 25 of friction surface 26 andthereby the automatic sear 13 is coupled to the semiautomatic sear 12.The arrangement of piston 20, and cylinder 19 with its accessories willbe simply called elastic engaging means 34.

In the inoperative position of inertia block 2 the bolt and inertiablock driving spring is compressed so that 'upon releasing said block 2,said spring 5 will drive said block 2 in the direction shown by arrow 33in Figure 4. -In other words upon pressing trigger 14, the coupledassembly of the automatic sear 13 and semi-automatic sear 12 will rotateabout pivot 11 and since the elastic engaging means 34 is coupling thesemi-automatic sear to the automatic sear, both heels and 27 willwithdraw from recess 9 whereby the sear engaging shoulder 7 is freed andthe block 2 moves forward in the direction shown by arrow 33 as can beclearly appreciated in Figure 5. At the same time the first spring 17and second spring 30 are starting to be compressed and while themovement of trigger 14 continues in the direction shown by arrow 35, aposition will be reached in which said first spring 17 is fullycompressed whereby a further rotation about pivot 11 of thesemi-automatic sear 12 is stopped, while the second spring 30 of theautomatic sear 13 is still not totally compressed, so that a furtherrotation about pivot 11 of the automatic sear 13 is still possible. Uponfurther rotating the automatic sear 13 (see Figure 6), the elasticengaging means 34 and more particularly piston disengages recess andthereby disconnects the semi-automatic sear 12 from the automatic sear13 and the first spring 17 immediately exerts an active pressure on base16 of housing 16 returning the semiautomatic sear 12 to its inoperativeposition. While these several steps are performed, the bolt of inertiablock 2 has fired and the gases have forced back, in the direction shownby arrow 36, the inertia block 2 against the opposition of the drivingspring 5 so that the first spring 17 will force to engage the flatsurface 15 of heel 15 with the sear engaging shoulder 7, and thus thefiring operation is stopped. As shown in Figure 6, the recess 9 issufficiently long to allow the insertion of heel 15 even if during thebackward movement of block 2 the latter is further back than necessaryfor the engagement of flat surface 15' with shoulder 7. Upon releasingtrigger 14, the automatic sear 13 returns to its inoperative position bythe action of compressed second spring and piston 20 again engagesrecess 25 so that the assembly adopts again the position as shown inFigure 3.

Repetition of the steps as above explained, will produce the firing ofanother shot.

It can thus be understood that the operation of the device is based onthe principle of providing an automatic sear and a semi-automatic searwhich may be temporarily coupled by means of the elastic engaging means34 and which automatic and semi-automatic sears have different momentsof rotation so that the semiautomatic sear will be uncoupled from theautomatic sear before the latter has accomplished its actuatingmovement. By actuating movement is to be understood the movement asshown by arrow 35, that is to say when the trigger is pressed by thefirer.

If the firing mechanism is to be used in automatic operation, that is tosay continuous or automatic firing, shaft 32 has to be operated fromoutside so that the selector 31, as shown in Figures 7 and 8 willconstantly maintain withdrawn the semi-automatic sear 12 and moreparticularly the first heel 15 from the recess 9 and more particularlyfrom the sear engaging shoulder 7. Upon operating trigger 14 that is tosay, upon withdrawing the second heel 27 from recess 9, as shown inFigure 8, the

inertia block 2 is free to continuously operate whilst the trigger 14and thereby the second heel 27, is maintained in its operative positionin which position piston 20 preferably engages recess 25 so that thetensile force exerted by second spring 311 on trigger 14 is decreased.However the tensile force of second spring 30 is sufiicient to overcomethe tensile force of spring 21 (see Figure 1) upon releasing trigger 14and thereby the inertia block 2 is stopped, because the second heel 27enters through opening 8 to engage the sear engaging shoulder 7.

it will be apparent to those skilled in the art that the same resultcould be obtained if the elastic engaging means 34 would be integralwith the automatic sear 13 and the recess 25 and friction surface 26would be provided by the semi-automatic sear 12.

in order to demonstrate that the principle of the firing mechanism asexplained above, may be applied to other embodiments, a furtherembodiment has been shown in Figure 2, wherein there is provided aninertia block housing 101, an inertia blocl 102, a spring guideprojection 103, an axis 104, a bolt and inertia block driving spring105, a platform 1%, a scar engaging shoulder 107, an opening 108, arecess 109 having a concave opposite end 110. The trigger and searsub-assembly consists of a pivot 111, a semi-automatic sear 112, anautomatic sear 113 having a trigger 114, a heel 115 having a flatsurface 115 for engaging the sear engaging shoulder 107. A first springhousing 116 and a first compression spring 117 and a spring guide 118; acylinder 119 and a piston 124), a spring 121 for urging said piston anda spring guide 122, a stop 123 and a recess 124, a second spring housing128, a second spring guide 129 and a second compression spring 131).Said piston 121i and accessories form an assembly hereinafter called theelastic engaging means 134.

All the above elements operate in exactly the same manner as describedin connection with the other embodiment shown in Figure l. The maindifference is that this embodiment shown in Figure 2 is preferably usedfor small arms and to this end the automatic sear 113 is simply atrigger 114 having two jaws or side plate members 137 and 138 (see alsoFigure 10) between which the semi-automatic sear 112 is housed and boththe automatic sear 113 and the semi-automatic sear 112 are swingablymounted on pivot 111. A transverse friction bar 139 is the substitutefor the friction surface 26 of the embodiment shown in Figure 1.

The operation of the device when operating as a semiautomatic device isexactly the same as that of the embodiment shown in Figure l and willtherefore not be described again.

If this device is to be operated as an automatic device, then stop 123,which is a slidable stop, can be displaced towards the opposite end ofrecess 124 with regard to the position shown in Figure 2, whereby piston120 is not able to penetrate into cylinder 119 and thus thesemiautomatic sear 112 is constantly coupled to the automatic sear 113and as long as the trigger 114 is operated, or depressed, the firing armwill operate as an automatic device or as a machine gun.

It is obvious that although in the above description reference has onlybeen made to an inertia block, that the latter can be replaced by anysuitable mechanism as, for example, a slidable percussion hammer.

Although reference is mainly made to small arms, it is obvious that thefiring mechanism of the present invention may be applied to any type ofautomatic-loading arms.

I claim:

1. A firing mechanism for automatic-loading arms such as sub-machineguns and the like firearms, comprising an inertia block housing havingan opening, an inertia block slidably housed in said housing and havinga sear engaging shoulder adapted to face said opening in its inoperativeposition, a semi-automatic sear and an automatic sear having triggermeans for operating said firing antenna mechanism, a pivot outside saidhousing and pivotally supporting said semi-automatic scar and saidautomatic sear, said semi-automatic sear having a first send and asecond end opposite 'sa'id pivot, said semi-automatic sear having a heelfor engaging said sear engaging shoulder through said opening, said heelbeing located at said first end, elastic engaging means supported by oneof said sears for temporarily coupling said semi-automatic and automaticsears, first spring means for said automatic sear in opposite workingrelationship with :regard to said trigger means, :and second springmeans for said semi-automatic sear located at said second end, forengaging said heel -with said sear engaging shoulder, and means fordriving said inertia bloc'k, said first spring means being arranged sothat it will be :fully compressed before said second spring means uponoperation of said trigger means to thereby block the pivotal movement ofsaid semi-automatic sear with respect to said automatic sear.

2. A firing mechanism for automatic loading arms such as sub-machineguns and the like firearms, comprising an inertia block housing having'an opening, an inertia block slidably housed in said housing and having-a single sear engaging shoulder adapted to face said opening in itsinoperative position, a pivoted semi-automatic sear and a pivotedautomatic sear, located at least partially outside said housing, saidsemi-automatic sear having a heel for engaging said sear engagingshoulder through said opening, engaging means supported 'by saidsemiautomatic sear and for-engaging said automatic sear, said automaticsear having trigger means for operating said firing mechanism, firstspring means for said semi-automatic sear for engaging said heel withsaid sear engaging shoulder, and second spring means :for said automaticsear in opposite working relationship with regard to said trigger means,and means for driving said inertia block, said first spring means beingarranged so that it will be fully compressed before said second springmeans upon operation of said trigger means to thereby block the pivotalmovement of said semi-automatic sear with respect to said automaticsear.

3. A firing mechanism for automatic loading arms such as sub-machineguns and the like firearms, comprising an inertia block housing havingan opening, an inertia block slidably housed in said housing and havinga sear engaging shoulder adapted to face said opening in its inoperativeposition, a pivot, .a semi-automatic sear and an automatic sear eachmounted on said pivot and located at least partially outside saidhousing, said semiautomatic sear having a heel for engaging said searengaging shoulder through said opening, engaging means, saidsemi-automatic sear supporting said engaging means for engaging saidautomatic sear, said automatic sear having trigger means for operatingsaid firing mechanism, first spring means for said semi-automatic searfor engaging said heel with :said sear engaging shoulder, and secondspring means for said automatic sear in-opposite working relationshipwith regard to said trigger means, and means for driving said inertiablock, said first spring means being arranged so that it will be fullycompressed before-said second spring means upon operation of saidtrigger means to thereby block .the pivotal movement of saidsemiautomatic sear with respect to said automatic sear.

4. A firing mechanism for automatic loading arms such as sub-machineguns and the like firearms, comprising an inertia block housing havingan opening an :inertia block slidably housed in said housing .and havinga scar engaging shoulder adapted to face said opening in its inoperativevposition, -a pivot, :a semi-automatic sear and an automatic sear eachmounted on said pivot and located at least partially outside saidhousing, said automatic sear being at least partially .hollowand saidsemiautomatic sear being at .least partially housed in said automaticsear, said semi-automaticsear having a .heel for engaging said searengaging shoulder through said 56 opening, engaging means, :saidsemi-automatic sear supporting said engaging means "for engaging saidautomatic sear, said automatic sear thaving trigger means fior operatingsaid firing mechanism, first spring means for said semi-automatic searfor engaging 'said heel with said sear engaging shoulder, and second:spring means for said automatic sear in opposite working relationshipwith regard :to said trigger :means, and means for driving said inertiablock, said first spring means being arranged so that it will be fullycompressed before said second spring means upon operation 'of saidtrigger means to thereby block the pivotal movement of saidsemi-automatic sear with respect to said automatic sear.

5 =A2firing mechanism forautomatic loading arms such as sub-machine gunsand the like firearms, cornprising an inertia block housing having anopening an inertia block slidably housed in said housing and having ascar engaging shoulder adapted to face said opening in its inoperativeposition, a pivot, .a semi-automatic scar and an automatic sear eachmounted on said pivot and located at least partially outside saidhousing, said semiautomatic .sear having a heel for engaging said searengaging shoulder through said opening, elastic engaging meanscomprising a cylinder integral with said semiautomatic sear, a springhoused Ill]. said cylinder, a piston partially housed in said cylinderand resiliently urged outwardly 'by said spring, said piston having ahead emerging out of said cylinder for engaging said auto,- matic sear,said automatic sear having trigger means for operating said firingmechanism, first spring means for said semi-automatic sear for engagingsaid heel with said sear engaging shoulder, and second spring means forsaid automatic sear in opposite working relationship with regard to saidtrigger means, and means for driving said inertia block, said firstspring means being arranged so that it will be fully compressed beforesaid second spring means upon operation of said trigger means 'tothereby block the pivotal movement of said semi-automatic sear withrespect to said automatic sear.

'6. A firing mechanism as claimed in claim 5, wherein said cylinderbeing provided with a stop, said piston 'is provided with a recess inwhich said stop is housed.

7. A firing mechanism for automatic loading arms such as sub-machineguns and the like firearms, comprising an inertia bl'ock housing anopening having an inertia block slidably housed in said housing andhaving a sear engaging shoulder adapted to face said opening .in itsinoperative position, a pivot, a semi-automatic sear and an automaticsear each mounted on said pivot and located at least partially outsidesaid housing, said semi-automatic sear having a heel for engaging saidsear engaging shoulder through said opening, elastic engaging meanscomprising a cylinder integral with said semi-automatic sear, a springhoused in said cylinder, a piston partially housed in said cylinder andresiliently urged outwardly 'by said spring, said piston .having a heademerging out of said cylinder, a friction surface 'having a recess -forming part of said semi-automatic sear said friction surface and recessbeing located in front of said head of said piston, said head beingcapable of engaging said recess, said automatic sear having triggermeans .for operating said firing mechanism, first spring means for saidsemiautomatic sear for engaging said heel with said sear engagingshoulder, second spring means for said automatic sear in oppositeworking relationship with regard to said trigger means, and means fordriving said inertia block, said first spring means being arranged sothat it wi'll be fully compressed before said second spring means uponoperation of said trigger means to thereby block the pivotal movement'of said semi-automatic sear with respect to said automaticsear.

8. Atfiring mechanism for automatic loading arms such as sub-machineguns and the like firearms, comprising-an inertia :block housing havingan opening an inertia block slidably housed in said housing and having ascar engaging shoulder adapted to face said opening in its inoperativeposition, a pivot, a semi-automatic sear and an automatic sear eachmounted on said pivot and located at least partially outside saidhousing, said semi-automatic sear having a heel for engaging said searengaging shoulder through said opening, said automatic sear havingtrigger means for operating said firing mechanism, first spring meansfor said semi-automatic sear for engaging said heel with said searengaging shoulder, and second spring means for said automatic sear inopposite working relationship with regard to said trigger means, saidautomatic sear comprises two separated side plate members, a transversefriction bar linking said two separated side plate members, saidsemi-automatic sear being partially housed between said two side platemembers, elastic engaging means, said semiautomatic sear supporting saidelastic engaging means for engaging said transverse friction bar of saidautomatic sear, and means for driving said inertia block, said firstspring means being arranged so that it will be fully compressed beforesaid second spring means upon operation of said trigger means to therebyblock the pivotal movement of said semi-automatic sear with respect tosaid automatic sear.

9. A firing mechanism for automatic loading arms such as sub-machineguns and the like firearms, comprising an inertia block housing havingan opening an inertia block slidably housed in said housing and having asear engaging shoulder adapted to face said opening in its inoperativeposition, a pivot, a semi-automatic scar and an automatic sear eachmounted on said pivot and located at least partially outside saidhousing, said semi-automatic sear having a heel for engaging said searengaging shoulder through said opening, said semi-automatic sear beingprovided with engaging means for engaging said automatic sear, saidautomatic sear having trigger means for operating said firing mechanism,said automatic sear comprises two separated side plate members, atransverse bar linking said two separated side plate members, saidsemiautomatic sear being partially housed between said two side platemembers, elastic engaging means, said semi-automatic sear supportingsaid elastic engaging means for engaging said transverse friction bar ofsaid automatic sear, first spring means for said semi-automatic sear,second spring means for said automatic sear, said second spring meanscomprising a second spring housing linked to said automatic sear andlocated behind said trigger means with regard to said pivot, a secondcompression spring partially housed in said second spring housing, asecond spring guide integral with said inertia block housing and guidingsaid second compression spring, said first spring means comprising afirst spring housing linked to said semi-automatic sear and locatedbehind said trigger means and behind said second spring housing withregard to said pivot, a first compression spring partially housed insaid first spring housing, a first spring guide integral with saidinertia block housing and guiding said first compression spring, saidfirst compression being so located and of such a length that it will betotally compressed before said second compression spring therebylimiting the pivotal movement of said semi-automatic sear in onedirection with respect to said automatic sear, and means for drivingsaid inertia block.

10. In a firing mechanism for automatic loading arms, a housing, aninertia block slidably mounted in said housing, a guide extending froman end of said block, a coil spring positioned in said housing andsuperimposed on said guide, said housing being provided with an openingtherein, said block having a recess including a concave portion and ashoulder registering with the opening in said housing, a pivot pinpositioned exteriorly of said housing, a semi-automatic sear supportedby said pivot pin, a hollow automatic sear surrounding saidsemi-automatic sear and including a trigger, said semi-automatic searincluding a heel adapted to engage said shoulder, and a casing, a coilspring positioned in said casing, a spring guide secured to said housingand projecting into said coil spring, said heel including a flat surfaceextending substantially parallel to said shoulder when saidsemiautomatic sear engages said shoulder, said semi-automatic searincluding a cylinder, a piston slidably mounted in said cylinder, aspring positioned in said cylinder and abutting said piston, there beinga recess in said piston, a stop member projecting into said recess forlimiting movement of said piston, said piston including an outer headengaging said automatic sear, said automatic sear including a secondheel having a flat surface substantially parallel to the flat surface onsaid first heel, a casing on said automatic sear, a coil springprojecting into said last named casing, a spring guide secured to saidhousing and projecting into said last named spring, and a selector forcontrolling said semi-automatic sear.

11. In a firing mechanism for automatic loading arms, a housing, ahammer means slidably mounted in said housing, a guide extending from anend of said hammer means, a coil spring positioned in said housing andsuper imposed on said guide, said housing being provided with an openingtherein, said hammer means having a recess including a concave portionand a shoulder registering with the opening in said housing, a pivot pinpositioned exteriorly of said housing, a semi-automatic sear supportedby said pivot pin, a hollow automatic sear surrounding saidsemi-automatic scar and including a trigger, said semi-automatic searincluding a heel adapted to engage said shoulder, and a casing, a coilspring positioned in said casing, a spring guide secured to said housingand projecting into said coil spring, said heel includ ing a flatsurface extending substantially parallel to said shoulder when saidsemi-automatic sear engages said shoulder, said semi-automatic searincluding a cylinder, a piston slidably mounted in said cylinder, aspring positioned in said cylinder and abutting said piston, there beinga recess in said piston, a stop member projecting into said recess forlimiting movement of said piston, said piston including an outer headengaging said automatic sear, said automatic sear including a secondheel having a fiat surface substantially parallel to the flat surface onsaid first heel, a casing on said automatic sear, a coil springprojecting into said last named casing, a spring guide secured to saidhousing and projecting into said last named spring, and a selector forcontrolling said semi-automatic sear.

12. A firing mechanism for automatic loading arms such as sub-machineguns and like fire arms, comprising an inertia block housing having anopening and an inertia block slidably housed in said housing and havinga scar engaging shoulder adapted to face said opening in its inoperativeposition, a pivot, a semi-automatic sear and an automatic sear, eachmounted on said pivot and located at least partially outside saidhousing, said semiautomatic sear having a heel for engaging said searengaging shoulder through said opening, elastic engaging meanscomprising a cylinder integral with said semiautomatic sear, a springhoused in said cylinder, a piston partially housed in said cylinder andresiliently urged outwardly by said spring, said piston having a heademerging out of said cylinder for engaging said automatic sear, saidautomatic sear having trigger means for operating said firing mechanism,first spring means for said semiautomatic sear for engaging said heelwith said sear engaging shoulder, and second spring means for saidautomatic sear in opposite working relationship with regard to saidtrigger means, and means for driving said inertia block, said firstspring means being arranged so that it will be fully compressed beforesaid second spring means upon operation of said trigger means to therebyblock the pivotal movement of said semi-automatic sear with respect tosaid automatic sear, said cylinder being provided with a stop, saidpiston being provided with a recess in which said stop is housed, andsaid stop being integral with said cylinder.

(References on following page) 9 References Cited in the file of thispatent 1,290,854 UNITED STATES PATENTS 985,156 Frommer Feb. 28, 19112539'447 1,083,872 Berthier Jan. 6, 1914 1,190,653 Hughes July 11, 191610 Sturgeon Jan. 7, 1919 Hoagland et a1. Nov. 1, 1938 Brewer Dec. 10,1940 Lochhead Jan. 30, 1951

